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• How to communicate between Client and Server in a Client-Server Application?

  - by Sanoj

  I would like to implement an Client-Server Application, where the business-logic, security validations and a database are at the server and the user interface are at the client. I would like to implement clients in different languages i.e. one in WPF/.NET, one Swing/Java , one in Android/Java and maybe one HTML/JavaScript client. The server will be on Internet, so I would like to be able to have encrypted communication. The client will send some lists of items to be added to the database, or update items, and do some transactions. The server will check if the items are already updated by another client, or update the item, add new items or delete items. How do I solve the communication between clients and the server in such a system? I have been thinking about: http/https webserver, and sending messages in JSON or XML and use Web Sockets for bi-directional communication. Use http in a RESTful way, except when WebSockets are needed. But I guess there are better solutions for native desktop applications than http? CORBA - I have just heard about it, and it's old and complex. Not much talk about it these days. XMPP/Jabber - I have just heard about it and I don't know if it fits me at all. EJabberd seams to be a popular implementation. AMQP - I have just heard about it and I don't know if it fits me at all. RabbitMQ seams to be a popular implementation. Windows Communication Foundation, Java RMI, Java Message Service - but are they language independent? I guess some of these alternatives are on different levels, maybe I can have i.e xmpp or amqp in web sockets over https? What technologys are used for this problem in companies today? and what is recommended to use? I have no experience of them other than webservers and http. Please give me some guidance in this jungle. What are the pros and cons of these technologies in my situation?

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• Castle ActiveRecord - schema generation without enforcing referential integrity?

  - by Simon

  Hi all, I've just started playing with Castle active record as it seems like a gentle way into NHibernate. I really like the idea of the database schema being generate from my classes during development. I want to do something similar to the following: [ActiveRecord] public class Camera : ActiveRecordBase<Camera> { [PrimaryKey] public int CameraId {get; set;} [Property] public int CamKitId {get; set;} [Property] public string serialNo {get; set;} } [ActiveRecord] public class Tripod : ActiveRecordBase<Tripod> { [PrimaryKey] public int TripodId {get; set;} [Property] public int CamKitId {get; set;} [Property] public string serialNo {get; set;} } [ActiveRecord] public class CameraKit : ActiveRecordBase<CameraKit> { [PrimaryKey] public int CamKitId {get; set;} [Property] public string description {get; set;} [HasMany(Inverse=true, Table="Cameras", ColumnKey="CamKitId")] public IList<Camera> Cameras {get; set;} [HasMany(Inverse=true, Table="Tripods", ColumnKey="CamKitId")] public IList<Camera> Tripods {get; set;} } A camerakit should contain any number of tripods and cameras. Camera kits exist independently of cameras and tripods, but are sometimes related. The problem is, if I use createschema, this will put foreign key constraints on the Camera and Tripod tables. I don't want this, I want to be able to to set CamKitId to null on the tripod and camera tables to indicate that it is not part of a CameraKit. Is there a way to tell activerecord/nhibernate to still see it as related, without enforcing the integrity? I was thinking I could have a cameraKit record in there to indicate "no camera kit", but it seems like oeverkill. Or is my schema wrong? Am I doing something I shouldn't with an ORM? (I've not really used ORMs much) Thanks!

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• Binary Search Help

  - by aloh

  Hi, for a project I need to implement a binary search. This binary search allows duplicates. I have to get all the index values that match my target. I've thought about doing it this way if a duplicate is found to be in the middle: Target = G Say there is this following sorted array: B, D, E, F, G, G, G, G, G, G, Q, R S, S, Z I get the mid which is 7. Since there are target matches on both sides, and I need all the target matches, I thought a good way to get all would be to check mid + 1 if it is the same value. If it is, keep moving mid to the right until it isn't. So, it would turn out like this: B, D, E, F, G, G, G, G, G, G (MID), Q, R S, S, Z Then I would count from 0 to mid to count up the target matches and store their indexes into an array and return it. That was how I was thinking of doing it if the mid was a match and the duplicate happened to be in the mid the first time and on both sides of the array. Now, what if it isn't a match the first time? For example: B, D, E, F, G, G, J, K, L, O, Q, R, S, S, Z Then as normal, it would grab the mid, then call binary search from first to mid-1. B, D, E, F, G, G, J Since G is greater than F, call binary search from mid+1 to last. G, G, J. The mid is a match. Since it is a match, search from mid+1 to last through a for loop and count up the number of matches and store the match indexes into an array and return. Is this a good way for the binary search to grab all duplicates? Please let me know if you see problems in my algorithm and hints/suggestions if any. The only problem I see is that if all the matches were my target, I would basically be searching the whole array but then again, if that were the case I still would need to get all the duplicates. Thank you BTW, my instructor said we cannot use Vectors, Hash or anything else. He wants us to stay on the array level and get used to using them and manipulating them.

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• How effective are technical test(s) and is it necessary?

  - by The Elite Gentleman

  Hi everyone, I recently took a Java technical test (for a company who wanted are looking for senior java developers) and, funny enough, I only realised the technical terms of what I've been doing all along after I've written the test. I'm not too IT jargon when it comes to development but I can pretty much code and create solutions unaware that I'm using design pattern (or the specifics of that design pattern) or technology. I learned things such as JMS, Frameworks, etc. while programming at home and having to google stuff online to problems I have. Others e.g. IoC, Surrogates in Databases, etc., I have used extensively without knowing that it had a name for it. Do you think that these technical test are effective and why? What interesting questions did you find that boggled your brains out while the clock kept ticking? Seeing that IT is vastly evolving at a rapid rate, do we have to constantly be updated with new terms that comes out? Some questions I was asked : What object oriented principle is violated by this architectural mechanism for dot notation? Is indexing tables effective for range query or point query search? What is ThreadLocal and what is it used for? Method overloading vs Method overriding. What is the difference between the 2? What is dynamic binding? Now, imagine my poor head trying to understand these jargons (considering I use it almost everyday) PS The question was not a programming question, where you have a problem and write code to solve it. Rather, a thinking type question and you write answers (against the clock). Update I clearly didn't come out clearly as I should have. There are those that are technically "book smart" but with very little hands-on experience and vice versa. So, the question (in connection to what I've asked) is that are these technical test seeking "book smart" people or people with lots of hands-on experience (some who are not that well clued up with too much book-smart jargons). How effective is it then, for companies to look for developers if most of the questions are too terminology-centric? (if that's the correct term, :))

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• Making a Grid in an NSView

  - by Hooligancat

  I currently have an NSView that draws a grid pattern (essentially a guide of horizontal and vertical lines) with the idea being that a user can change the spacing of the grid and the color of the grid. The purpose of the grid is to act as a guideline for the user when lining up objects. Everything works just fine with one exception. When I resize the NSWindow by dragging the resize handle, if my grid spacing is particularly small (say 10 pixels). the drag resize becomes lethargic in nature. My drawRect code for the grid is as follows: -(void)drawRect:(NSRect)dirtyRect { NSRect thisViewSize = [self bounds]; // Set the line color [[NSColor colorWithDeviceRed:0 green:(255/255.0) blue:(255/255.0) alpha:1] set]; // Draw the vertical lines first NSBezierPath * verticalLinePath = [NSBezierPath bezierPath]; int gridWidth = thisViewSize.size.width; int gridHeight = thisViewSize.size.height; int i; while (i < gridWidth) { i = i + [self currentSpacing]; NSPoint startPoint = {i,0}; NSPoint endPoint = {i, gridHeight}; [verticalLinePath setLineWidth:1]; [verticalLinePath moveToPoint:startPoint]; [verticalLinePath lineToPoint:endPoint]; [verticalLinePath stroke]; } // Draw the horizontal lines NSBezierPath * horizontalLinePath = [NSBezierPath bezierPath]; i = 0; while (i < gridHeight) { i = i + [self currentSpacing]; NSPoint startPoint = {0,i}; NSPoint endPoint = {gridWidth, i}; [horizontalLinePath setLineWidth:1]; [horizontalLinePath moveToPoint:startPoint]; [horizontalLinePath lineToPoint:endPoint]; [horizontalLinePath stroke]; } } I suspect this is entirely to do with the way that I am drawing the grid and am open to suggestions on how I might better go about it. I can see where the inefficiency is coming in, drag-resizing the NSWindow is constantly calling the drawRect in this view as it resizes, and the closer the grid, the more calculations per pixel drag of the parent window. I was thinking of hiding the view on the resize of the window, but it doesn't feel as dynamic. I want the user experience to be very smooth without any perceived delay or flickering. Does anyone have any ideas on a better or more efficient method to drawing the grid? All help, as always, very much appreciated.

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• PHP-based LaTeX parser -- where to begin?

  - by Alex Basson

  The project: I want to build a LaTeX-to-MathML translator in PHP. Why? Because I'm a mathematician, and I want to publish math on my Drupal site. It doesn't have to translate all of LaTeX, since the basic document-level stuff is ably handled by the CMS and wouldn't be written in LaTeX to begin with; it just has to translate math written in LaTeX into math written in MathML. Although I feel as though I've done my due diligence, this doesn't seem to exist already. Maybe I'm wrong---if you know of something that would serve this purpose, by all means let me know, and thank you in advance. But assuming it doesn't exist, I guess I have to go write it myself. Here's the thing, though: I've never done anything this ambitious. I don't really know where to begin. I've used PHP for years, but just to do the standard "build a CMS with PHP and MySQL"-type of stuff. I've never attempted anything as seemingly sophisticated as translation from one language to another. I'm just dumb enough to consider doing it with regex---after all, LaTeX is a much more formal language, and it doesn't allow for nearly the kinds of pathological edge-cases, as say, HTML. But on the other hand, I'm just smart enough to realize this is probably a terrible idea: now I have two problems, and I sure don't want to end up like this guy. So if that's not the way to go (right?), what is? How should I start thinking about this problem? Am I essentially writing a LaTeX compiler in PHP, and if so, what do I need to know to do that (like, should I just go read the Purple Dragon book first?)? I'm both really excited and pretty intimidated by the prospect of this project, but hey, this is how we all learn to be programmers, right? If something we need doesn't exist, we go and build it, necessity is the mother of... you get the point. Tremendous thanks to everyone in advance for any and all guidance you can offer.

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• Finding what makes strings unique in a list, can you improve on brute force?

  - by Ed Guiness

  Suppose I have a list of strings where each string is exactly 4 characters long and unique within the list. For each of these strings I want to identify the position of the characters within the string that make the string unique. So for a list of three strings abcd abcc bbcb For the first string I want to identify the character in 4th position d since d does not appear in the 4th position in any other string. For the second string I want to identify the character in 4th position c. For the third string it I want to identify the character in 1st position b AND the character in 4th position, also b. This could be concisely represented as abcd -> ...d abcc -> ...c bbcb -> b..b If you consider the same problem but with a list of binary numbers 0101 0011 1111 Then the result I want would be 0101 -> ..0. 0011 -> .0.. 1111 -> 1... Staying with the binary theme I can use XOR to identify which bits are unique within two binary numbers since 0101 ^ 0011 = 0110 which I can interpret as meaning that in this case the 2nd and 3rd bits (reading left to right) are unique between these two binary numbers. This technique might be a red herring unless somehow it can be extended to the larger list. A brute-force approach would be to look at each string in turn, and for each string to iterate through vertical slices of the remainder of the strings in the list. So for the list abcd abcc bbcb I would start with abcd and iterate through vertical slices of abcc bbcb where these vertical slices would be a | b | c | c b | b | c | b or in list form, "ab", "bb", "cc", "cb". This would result in four comparisons a : ab -> . (a is not unique) b : bb -> . (b is not unique) c : cc -> . (c is not unique) d : cb -> d (d is unique) or concisely abcd -> ...d Maybe it's wishful thinking, but I have a feeling that there should be an elegant and general solution that would apply to an arbitrarily large list of strings (or binary numbers). But if there is I haven't yet been able to see it. I hope to use this algorithm to to derive minimal signatures from a collection of unique images (bitmaps) in order to efficiently identify those images at a future time. If future efficiency wasn't a concern I would use a simple hash of each image. Can you improve on brute force?

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• All embedded databases fail to open connections

  - by rsteckly

  Hi, I'm working on a winforms desktop application that needs to store data. I made the really bad decision to try and embed a database. I've tried: SQLite VistaDB SQL Server Compact In each case, I was able to generate a Entity Framework Model over the basic schema I've created. I have an event that adds data that I've been using to test these databases. Well, I kept adding a new record using EF and finding it didn't actually insert a record. In debugging, I checked the context object to see what was happening. It turns out that it is saying "the underlying provider failed to open," or something to that effect. It was not throwing an exception, just not inserting a record. The same thing has happened for all 3 embedded databases--prompting me to get it through my dense head that there has to be something wrong with my configuration. Well, I tried to write some basic sql using a sqlconnection and sqlcommand. This time it throws an exception. In the SQL Server Compact case, it now says: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) I thought perhaps a problem was the path in app.Config. So I changed the connection string to: Note that I simplified the path away from anything that might have spaces and avoided using the Data Directory nonsense that causes problem when the debugging directory does not match the preconfigured value for the data directory. I'm running Windows 7; I thought perhaps it might be an access issue--so I tried running VS 2010 in Administrator mode. No luck. I also installed Sql Server Compact SP2, thinking this might be a bug. No luck. Anyway, I'm ready to pull my hair out. I'm on a tight deadline for this thing and didn't expect to spend the day trying to figure out what is going on.

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• Best Practice: Legitimate Cross-Site Scripting

  - by Ryan

  While cross-site scripting is generally regarded as negative, I've run into several situations where it's necessary. I was recently working within the confines of a very limiting content management system. I needed to include database code within the page, but the hosting server didn't have anything usable available. I set up a couple barebones scripts on my own server, originally thinking that I could use AJAX to import the contents of my scripts directly into the template of the CMS (thus retaining dynamic images, menu items, CSS, etc.). I was wrong. Due to the limitations of XMLHttpRequest objects, it's not possible to grab content from a different domain. So I thought "iFrame" - even though I'm not a fan of frames, I thought that I could create a frame that matched the width and height of the content, so that it would appear native. Again, I was blocked by cross-site scripting "protections." While I could indeed load a remote file into the iFrame, I couldn't execute JavaScript to modify its size on either the host page or inside the loaded page. In this particular scenario, I wasn't able to point a subdomain to my server. I also couldn't create a script on the CMS server that could proxy content from my server, so my last thought was to use a remote JavaScript. A remote JavaScript works. It breaks when the user has JavaScript disabled, which is a downside; but it works. The "problem" I was having with using a remote JavaScript was that I had to use the JS function document.write() to output any content. Any output that isn't JS causes script errors. In addition to using document.write() for every line, you also have to ensure that the content is escaped - or else you end up with more script errors. My solution was as follows: My script received a GET parameter ("page") and then looked for the file ({$page}.php), and read the contents into a variable. However, I had to use awkward buffering techniques in order to actually execute the included scripts (for things like database interaction) then strip the final content of all line break characters ("\n") followed by escaping all required characters. The end result is that my original script (which outputs JavaScript) accesses seemingly "standard" scripts on my server and converts their standard output to JavaScript for displaying within the CMS template. While this solution works, it seems like there may be a better way to accomplish the same thing. What is the best way to make cross-site scripting work specifically for the purpose of including content from a completely different domain?

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• What to Return? Error String, Bool with Error String Out, or Void with Exception

  - by Ranger Pretzel

  I spend most of my time in C# and am trying to figure out which is the best practice for handling an exception and cleanly return an error message from a called method back to the calling method. For example, here is some ActiveDirectory authentication code. Please imagine this Method as part of a Class (and not just a standalone function.) bool IsUserAuthenticated(string domain, string user, string pass, out errStr) { bool authentic = false; try { // Instantiate Directory Entry object DirectoryEntry entry = new DirectoryEntry("LDAP://" + domain, user, pass); // Force connection over network to authenticate object nativeObject = entry.NativeObject; // No exception thrown? We must be good, then. authentic = true; } catch (Exception e) { errStr = e.Message().ToString(); } return authentic; } The advantages of doing it this way are a clear YES or NO that you can embed right in your If-Then-Else statement. The downside is that it also requires the person using the method to supply a string to get the Error back (if any.) I guess I could overload this method with the same parameters minus the "out errStr", but ignoring the error seems like a bad idea since there can be many reasons for such a failure... Alternatively, I could write a method that returns an Error String (instead of using "out errStr") in which a returned empty string means that the user authenticated fine. string AuthenticateUser(string domain, string user, string pass) { string errStr = ""; try { // Instantiate Directory Entry object DirectoryEntry entry = new DirectoryEntry("LDAP://" + domain, user, pass); // Force connection over network to authenticate object nativeObject = entry.NativeObject; } catch (Exception e) { errStr = e.Message().ToString(); } return errStr; } But this seems like a "weak" way of doing things. Or should I just make my method "void" and just not handle the exception so that it gets passed back to the calling function? void AuthenticateUser(string domain, string user, string pass) { // Instantiate Directory Entry object DirectoryEntry entry = new DirectoryEntry("LDAP://" + domain, user, pass); // Force connection over network to authenticate object nativeObject = entry.NativeObject; } This seems the most sane to me (for some reason). Yet at the same time, the only real advantage of wrapping those 2 lines over just typing those 2 lines everywhere I need to authenticate is that I don't need to include the "LDAP://" string. The downside with this way of doing it is that the user has to put this method in a try-catch block. Thoughts? Is there another way of doing this that I'm not thinking of?

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• What does Ruby have that Python doesn't, and vice versa?

  - by Lennart Regebro

  There is a lot of discussions of Python vs Ruby, and I all find them completely unhelpful, because they all turn around why feature X sucks in language Y, or that claim language Y doesn't have X, although in fact it does. I also know exactly why I prefer Python, but that's also subjective, and wouldn't help anybody choosing, as they might not have the same tastes in development as I do. It would therefore be interesting to list the differences, objectively. So no "Python's lambdas sucks". Instead explain what Ruby's lambdas can do that Python's can't. No subjectivity. Example code is good! Don't have several differences in one answer, please. And vote up the ones you know are correct, and down those you know are incorrect (or are subjective). Also, differences in syntax is not interesting. We know Python does with indentation what Ruby does with brackets and ends, and that @ is called self in Python. UPDATE: This is now a community wiki, so we can add the big differences here. Ruby has a class reference in the class body In Ruby you have a reference to the class (self) already in the class body. In Python you don't have a reference to the class until after the class construction is finished. An example: class Kaka puts self end self in this case is the class, and this code would print out "Kaka". There is no way to print out the class name or in other ways access the class from the class definition body in Python. All classes are mutable in Ruby This lets you develop extensions to core classes. Here's an example of a rails extension: class String def starts_with?(other) head = self[0, other.length] head == other end end Ruby has Perl-like scripting features Ruby has first class regexps, $-variables, the awk/perl line by line input loop and other features that make it more suited to writing small shell scripts that munge text files or act as glue code for other programs. Ruby has first class continuations Thanks to the callcc statement. In Python you can create continuations by various techniques, but there is no support built in to the language. Ruby has blocks With the "do" statement you can create a multi-line anonymous function in Ruby, which will be passed in as an argument into the method in front of do, and called from there. In Python you would instead do this either by passing a method or with generators. Ruby: amethod { |here| many=lines+of+code goes(here) } Python: def function(here): many=lines+of+code goes(here) amethod(function) Interestingly, the convenience statement in Ruby for calling a block is called "yield", which in Python will create a generator. Ruby: def themethod yield 5 end themethod do |foo| puts foo end Python: def themethod(): yield 5 for foo in themethod: print foo Although the principles are different, the result is strikingly similar. Python has built-in generators (which are used like Ruby blocks, as noted above) Python has support for generators in the language. In Ruby you could use the generator module that uses continuations to create a generator from a block. Or, you could just use a block/proc/lambda! Moreover, in Ruby 1.9 Fibers are, and can be used as, generators. docs.python.org has this generator example: def reverse(data): for index in range(len(data)-1, -1, -1): yield data[index] Contrast this with the above block examples. Python has flexible name space handling In Ruby, when you import a file with require, all the things defined in that file will end up in your global namespace. This causes namespace pollution. The solution to that is Rubys modules. But if you create a namespace with a module, then you have to use that namespace to access the contained classes. In Python, the file is a module, and you can import its contained names with from themodule import *, thereby polluting the namespace if you want. But you can also import just selected names with from themodule import aname, another or you can simply import themodule and then access the names with themodule.aname. If you want more levels in your namespace you can have packages, which are directories with modules and an __init__.py file. Python has docstrings Docstrings are strings that are attached to modules, functions and methods and can be introspected at runtime. This helps for creating such things as the help command and automatic documentation. def frobnicate(bar): """frobnicate takes a bar and frobnicates it >>> bar = Bar() >>> bar.is_frobnicated() False >>> frobnicate(bar) >>> bar.is_frobnicated() True """ Python has more libraries Python has a vast amount of available modules and bindings for libraries. Python has multiple inheritance Ruby does not ("on purpose" -- see Ruby's website, see here how it's done in Ruby). It does reuse the module concept as a sort of abstract classes. Python has list/dict comprehensions Python: res = [x*x for x in range(1, 10)] Ruby: res = (0..9).map { |x| x * x } Python: >>> (x*x for x in range(10)) <generator object <genexpr> at 0xb7c1ccd4> >>> list(_) [0, 1, 4, 9, 16, 25, 36, 49, 64, 81] Ruby: p = proc { |x| x * x } (0..9).map(&p) Python: >>> {x:str(y*y) for x,y in {1:2, 3:4}.items()} {1: '4', 3: '16'} Ruby: >> Hash[{1=>2, 3=>4}.map{|x,y| [x,(y*y).to_s]}] => {1=>"4", 3=>"16"} Python has decorators Things similar to decorators can be created in Ruby, and it can also be argued that they aren't as necessary as in Python.

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• Calling an Excel Add-In method from C# application or vice versa

  - by Jude

  I have an Excel VBA add-in with a public method in a bas file. This method currently creates a VB6 COM object, which exists in a running VB6 exe/vbp. The VB6 app loads in data and then the Excel add-in method can call methods on the VB6 COM object to load the data into an existing Excel xls. This is all currently working. We have since converted our VB6 app to C#. My question is: What is the best/easiest way to mimic this behavior with the C#/.NET app? I'm thinking I may not be able to pull the data from the .NET app into Excel from the add-in method since the .Net app needs to be running with data loaded (so no using a stand-alone C# class library). Maybe we can, instead, push the data from .NET to Excel by accessing the VBA add-in method from the C# code? The following is the existing VBA method accessing the VB6 app: Public Sub UpdateInDataFromApp() Dim wkbInData As Workbook Dim oFPW As Object Dim nMaxCols As Integer Dim nMaxRows As Integer Dim j As Integer Dim sName As String Dim nCol As Integer Dim nRow As Integer Dim sheetCnt As Integer Dim nDepth As Integer Dim sPath As String Dim vData As Variant Dim SheetRange As Range Set wkbInData = wkbOpen("InData.xls") sPath = g_sPathXLSfiles & "\" 'Note: the following will bring up fpw app if not already running Set oFPW = CreateObject("FPW.CProfilesData") If oFPW Is Nothing Then MsgBox "Unable to reference " & sApp Else . . . sheetCnt = wkbInData.Sheets.Count 'get number of sheets in indata workbook For j = 2 To sheetCnt 'set counter to loop over all sheets except the first one which is not input data fields With wkbInData.Worksheets(j) Set SheetRange = .UsedRange End With With SheetRange nMaxRows = .Rows.Count 'get range of sheet(j) nMaxCols = .Columns.Count 'get range of sheet(j) Range(.Cells(2, 2), .Cells(nMaxRows, nMaxCols)).ClearContents 'Clears data from data range (51 Columns) Range(.Cells(2, 2), .Cells(nMaxRows, nMaxCols)).ClearComments End With With oFPW 'vb6 object For nRow = 2 To nMaxRows ' loop through rows sName = SheetRange.Cells(nRow, 1) 'Field name vData = .vntGetSymbol(sName, 0) 'Check if vb6 app identifies the name nDepth = .GetInputTableDepth(sName) 'Get number of data items for this field name from vb6 app nMaxCols = nDepth + 2 'nDepth=0, is single data item For nCol = 2 To nMaxCols 'loop over deep screen fields nDepth = nCol - 2 'current depth vData = .vntGetSymbol(sName, nDepth) 'Get Data from vb6 app If LenB(vData) > 0 And IsNumeric(vData) Then 'Check if data returned SheetRange.Cells(nRow, nCol) = vData 'Poke the data in Else SheetRange.Cells(nRow, nCol) = vData 'Poke a zero in End If Next 'nCol Next 'nRow End With Set SheetRange = Nothing Next 'j End If Set wkbInData = Nothing Set oFPW = Nothing Exit Sub . . . End Sub Any help would be appreciated.

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• SaaS Architecture Question from Newbie

  - by user226767

  I have developed a number of departmental client-server applications, and am now ready to begin working on moving one of these applications to a SaaS model. I have done some basic web development, but I'm a newbie when it comes to SaaS architectures. One of the first questions that comes to mind as I try to design the architecture is the question of single vs. multi tenancy. The pros and cons of each vary significantly depending on the type of application and scale required, so I'd like to describe my application and scale needs below, and hope others can comment on how I should get started with the architecture. The client-server application currently consists of a Firebird database and a Windows application. The database contains about 20 tables containing a few thousand records in 4 primary tables, and a few hundred records in various lookup and related tables. Although the number of records is small, the size can get large, as the database can contain large BLOBS. Each customer sets up their own database and has a handful of users within the organization connected to it. When I update the db schema, a new windows application is released, and it checks the db schema and then applies the updates as needed. For the SaaS application, I am designing for 100's (not 1000's or millions) of new customers per year. My first thought was to go with a multi tenancy model to make updates easy (shut down apply the updates to one database, and then start up). On the other hand, a single tenancy model would provide a means to roll updates out to a group of customers at a time, and spread the risk of data corruption - i.e. if something goes wrong with a database, it will impact one customer instead of all customers. With this idea, I was thinking of having a single web front-end which would connect to a single customer database upon login. Thus, when a new customer creates an account, a new database would be created (each customer would have their own db with multiple users as needed for the customer). In this model, a db update would require either a process to go through each db to apply schema changes, or a trigger upon logging in to initiate a schema update similar to the client-server model currently in use. Can anyone point me to information for similar applications which have been ported from client-server to SaaS? Or provide any pointers to consider? Basically I'm looking for architecture examples of taking a departmental application and making it available as a self service website for multiple customers. Thanks for any suggestions, resources, etc.

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• Searches (and general querying) with HBase and/or Cassandra (best practices?)

  - by alexeypro

  I have User model object with quite few fields (properties, if you wish) in it. Say "firstname", "lastname", "city" and "year-of-birth". Each user also gets "unique id". I want to be able to search by them. How do I do that properly? How to do that at all? My understanding (will work for pretty much any key-value storage -- first goes key, then value) u:123456789 = serialized_json_object ("u" as a simple prefix for user's keys, 123456789 is "unique id"). Now, thinking that I want to be able to search by firstname and lastname, I can save in: f:Steve = u:384734807,u:2398248764,u:23276263 f:Alex = u:12324355,u:121324334 so key is "f" - which is prefix for firstnames, and "Steve" is actual firstname. For "u:Steve" we save as value all user id's who are "Steve's". That makes every search very-very easy. Querying by few fields (properties) -- say by firstname (i.e. "Steve") and lastname (i.e. "l:Anything") is still easy - first get list of user ids from "f:Steve", then list from "l:Anything", find crossing user ids, an here you go. Problems (and there are quite a few): Saving, updating, deleting user is a pain. It has to be atomic and consistent operation. Also, if we have size of value limited to some value - then we are in (potential) trouble. And really not of an answer here. Only zipping the list of user ids? Not too cool, though. What id we want to add new field to search by. Eventually. Say by "city". We certainly can do the same way "c:Los Angeles" = ..., "c:Chicago" = ..., but if we didn't foresee all those "search choices" from the very beginning, then we will have to be able to create some night job or something to go by all existing User records and update those "c:CITY" for them... Quite a big job! Problems with locking. User "u:123" updates his name "Alex", and user "u:456" updates his name "Alex". They both have to update "f:Alex" with their id's. That means either we get into overwriting problem, or one update will wait for another (and imaging if there are many of them?!). What's the best way of doing that? Keeping in mind that I want to search by many fields? P.S. Please, the question is about HBase/Cassandra/NoSQL/Key-Value storages. Please please - no advices to use MySQL and "read about" SELECTs; and worry about scaling problems "later". There is a reason why I asked MY question exactly the way I did. :-)

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• Google OAuthGetRequestToken returns "signature_invalid"

  - by M Schenkel

  Trying for hours to get a request token using Google OAuthGetRequestToken but it always returns "signature_invalid". For a test I use the oAuth Playground to successfully request the token. Here are the results: Signature base string GET&https%3A%2F%2Fwww.google.com%2Faccounts%2FOAuthGetRequestToken&oauth_callback%3Dhttp%253A%252F%252Fgooglecodesamples.com%252Foauth_playground%252Findex.php%26oauth_consumer_key%3Dwww.embeddedanalytics.com%26oauth_nonce%3D56aa884162ed21815a0406725c79cf79%26oauth_signature_method%3DRSA-SHA1%26oauth_timestamp%3D1321417095%26oauth_version%3D1.0%26scope%3Dhttps%253A%252F%252Fwww.google.com%252Fanalytics%252Ffeeds%252F Request/Response GET /accounts/OAuthGetRequestToken?scope=https%3A%2F%2Fwww.google.com%2Fanalytics%2Ffeeds%2F HTTP/1.1 Host: www.google.com Accept: */* Authorization: OAuth oauth_version="1.0", oauth_nonce="56aa884162ed21815a0406725c79cf79", oauth_timestamp="1321417095", oauth_consumer_key="www.embeddedanalytics.com", oauth_callback="http%3A%2F%2Fgooglecodesamples.com%2Foauth_playground%2Findex.php", oauth_signature_method="RSA-SHA1", oauth_signature="qRtorIaSFaQdOXW1u6eMQlY9LT2j7ThG5kgkcD6rDcW4MIvzluslFgYRNTuRvnaruraNpItjojtgsrK9deYRKoHBGOlU27SsWy6jECxKczcSECl3cVAcjk7dvbywFMDkgi1ZhTZ5Q%2BFoD60HoVQUYnGUbOO0jPXI48LfkiA5ZN4%3D" HTTP/1.1 200 OK Content-Type: text/plain; charset=UTF-8 Date: Wed, 16 Nov 2011 04:18:15 GMT Expires: Wed, 16 Nov 2011 04:18:15 GMT Cache-Control: private, max-age=0 X-Content-Type-Options: nosniff X-XSS-Protection: 1; mode=block Content-Length: 118 Server: GSE oauth_token=4%2FmO86qZzixayI2NoUc-hewC--D53R&oauth_token_secret=r0PReF9D83w1d6uP0nyQQm9c&oauth_callback_confirmed=true I am using Fiddler to trace my calls. It returns the Signature base string: GET&https%3A%2F%2Fwww.google.com%2Faccounts%2FOAuthGetRequestToken&oauth_callback%3Dhttp%253A%252F%252Fgooglecodesamples.com%252Foauth_playground%252Findex.php%26oauth_consumer_key%3Dwww.embeddedanalytics.com%26oauth_nonce%3Dl9Jydzjyzt2fJfM3ltY5yrxxYy2uh1U7%26oauth_signature_method%3DRSA-SHA1%26oauth_timestamp%3D1321417107%26oauth_version%3D1.0%26scope%3Dhttps%253A%252F%252Fwww.google.com%252Fanalytics%252Ffeeds%252F Aside from the oauth_timestamp and oauth_nonce (which should be different), the base string are pretty much identical. Anyone know what I am doing wrong? Update 11/20/2011 Thinking it might be something wrong with my RSA-SHA signing, I have since tried HMAC-SHA. It gives the same results. I thought it might be beneficial to include the Fiddler results (I added carriage returns to have it format better). GET https://www.google.com/accounts/OAuthGetRequestToken? scope=https%3A%2F%2Fwww.google.com%2Fanalytics%2Ffeeds%2F HTTP/1.1 Content-Type: application/x-www-form-urlencoded Authorization: OAuth oauth_version="1.0", oauth_nonce="7C4C900EAACC9C7B62E399A91B81D8DC", oauth_timestamp="1321845418", oauth_consumer_key="www.embeddedanalytics.com", oauth_signature_method="HMAC-SHA1", oauth_signature="ows%2BbFTNSR8jVZo53rGBB8%2BfwFM%3D" Host: www.google.com Accept: */* Accept-Encoding: identity Response HTTP/1.1 400 Bad Request Content-Type: text/plain; charset=UTF-8 Date: Mon, 21 Nov 2011 03:16:57 GMT Expires: Mon, 21 Nov 2011 03:16:57 GMT Cache-Control: private, max-age=0 X-Content-Type-Options: nosniff X-XSS-Protection: 1; mode=block Content-Length: 358 Server: GSE signature_invalid base_string:GET&https%3A%2F%2Fwww.google.com%2Faccounts%2FOAuthGetRequestToken &oauth_consumer_key%3Dwww.embeddedanalytics.com %26oauth_nonce%3D7C4C900EAACC9C7B62E399A91B81D8DC %26oauth_signature_method%3DHMAC-SHA1 %26oauth_timestamp%3D1321845418 %26oauth_version%3D1.0 %26scope%3Dhttps%253A%252F%252Fwww.google.com%252Fanalytics%252Ffeeds%252F

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• Would someone mind giving suggestions for this new assembly language?

  - by Noctis Skytower

  Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo save Store load Retrieve L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller exit End the program print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

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• WordPress Write Cache Problem with Multiple Sessions

  - by Volomike

  I'm working on a content dripper custom plugin in WordPress that my client asked me to build. He says he wants it to catch a page view event, and if it's the right time of day (24 hours since last post), to pull from a resource file and output another post. He needed it to also raise a flag and prevent other sessions from firing that same snippet of code. So, raise some kind of flag saying, "I'm posting that post, go away other process," and then it makes that post and releases the flag again. However, the strangest thing is occurring when placed under load with multiple sessions hitting the site with page views. It's firing instead of one post -- it's randomly doing like 1, 2, or 3 extra posts, with each one thinking that it was the right time to post because it was 24 hours past the time of the last post. Because it's somewhat random, I'm guessing that the problem is some kind of write caching where the other sessions don't see the raised flag just yet until a couple microseconds pass. The plugin was raising the "flag" by simply writing to the wp_options table with the update_option() API in WordPress. The other user sessions were supposed to read that value with get_option() and see the flag, and then not run that piece of code that creates the post because a given session was already doing it. Then, when done, I lower the flag and the other sessions continue as normal. But what it's doing is letting those other sessions in. To make this work, I was using add_action('loop_start','checkToAddContent'). The odd thing about that function though is that it's called more than once on a page, and in fact some plugins may call it. I don't know if there's a better event to hook. Even still, even if I find an event to hook that only runs once on a page view, I still have multiple sessions to contend with (different users who may view the page at the same time) and I want only one given session to trigger the content post when the post is due on the schedule. I'm wondering if there are any WordPress plugin devs out there who could suggest another event hook to latch on to, and to figure out another way to raise a flag that all sessions would see. I mean, I could use the shared memory API in PHP, but many hosting plans have that disabled. Can't use a cookie or session var because that's only one single session. About the only thing that might work across hosting plans would be to drop a file as a flag, instead. If the file is present, then one session has the flag. If the file is not present, then other sessions can attempt to get the flag. Sure, I could use the file route, but it's kind of immature in my opinion and I was wondering if there's something in WordPress I could do.

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• How to designing a generic databse whos layout may change over time?

  - by mawg

  Here's a tricky one - how do I programatically create and interrogate a database who's contents I can't really foresee? I am implementing a generic input form system. The user can create PHP forms with a WYSIWYG layout and use them for any purpose he wishes. He can also query the input. So, we have three stages: a form is designed and generated. This is a one-off procedure, although the form can be edited later. This designs the database. someone or several people make use of the form - say for daily sales reports, stock keeping, payroll, etc. Their input to the forms is written to the database. others, maybe management, can query the database and generate reports. Since these forms are generic, I can't predict the database structure - other than to say that it will reflect HTML form fields and consist of a the data input from collection of edit boxes, memos, radio buttons and the like. Questions and remarks: A) how can I best structure the database, in terms of tables and columns? What about primary keys? My first thought was to use the control name to identify each column, then I realized that the user can edit the form and rename, so that maybe "name" becomes "employee" or "wages" becomes ":salary". I am leaning towards a unique number for each. B) how best to key the rows? I was thinking of a timestamp to allow me to query and a column for the row Id from A) C) I have to handle column rename/insert/delete. Foe deletion, I am unsure whether to delete the data from the database. Even if the user is not inputting it from the form any more he may wish to query what was previously entered. Or there may be some legal requirements to retain the data. Any gotchas in column rename/insert/delete? D) For the querying, I can have my PHP interrogate the database to get column names and generate a form with a list where each entry has a database column name, a checkbox to say if it should be used in the query and, based on column type, some selection criteria. That ought to be enough to build searches like "position = 'senior salesman' and salary 50k". E) I probably have to generate some fancy charts - graphs, histograms, pie charts, etc for query results of numerical data over time. I need to find some good FOSS PHP for this. F) What else have I forgotten? This all seems very tricky to me, but I am database n00b - maybe it is simple to you gurus?

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• The iPhone “phone” doesn’t have the provisioning profile with which the application was signed.

  - by eda

  i have tried everything to fix this provision problem and nothing is working. ive reformated my mac, reinstalled the iphone, ive also dragged the provisions (developer and distribution) onto the organizer, itunes, and xcode. in itunes people say to drag the provisions to the iphone icon but that doesnt work its only able to go under library it shows a blue rectangle for me to drop it there. i just have a newly created dummy app with a 57x57 icon. ive also setup the project with the distribution thing with its distribution provision. when i build i get this: The iPhone “myphone” doesn’t have the provisioning profile with which the application was signed. Click “Install and Run” to install the provisioning profile “distribution” on “myphone” and continue running “helloworld.app”. and it has a button "install and run" ive clicked on that hundreths of times and nothing. in orgranizer i see a tab called console ive cleared it and rebuild the app and there is some output that i dont understand. I'm thinking its my problem whats it mean? Fri Mar 26 11:22:19 unknown misagent[215] <Error>: profile not valid: 0xe8008012 Fri Mar 26 11:22:19 unknown mobile_installationd[206] <Error>: 00808600 install_embedded_profile: Skipping the installation of the embedded profile Fri Mar 26 11:22:20 unknown mobile_installationd[206] <Error>: 00808600 verify_executable: Could not validate signature: e8008015 Fri Mar 26 11:22:20 unknown mobile_installationd[206] <Error>: 00808600 preflight_application_install: Could not verify /var/tmp/install_staging.NEb61T/helloworld.app/helloworld Fri Mar 26 11:22:20 unknown mobile_installationd[206] <Error>: 00808600 install_application: Could not preflight application install Fri Mar 26 11:22:20 unknown mobile_installation_proxy[219] <Error>: handle_install: Installation failed Fri Mar 26 11:22:20 unknown mobile_installationd[206] <Error>: 00808600 handle_install: API failed Fri Mar 26 11:22:20 unknown mobile_installationd[206] <Error>: 00808600 send_message: failed to send mach message of 64 bytes: 10000003 Fri Mar 26 11:22:20 unknown mobile_installationd[206] <Error>: 00808600 send_error: Could not send error response to client Fri Mar 26 11:22:42 unknown misagent[231] <Error>: profile not valid: 0xe8008012 Fri Mar 26 11:22:43 unknown mobile_installationd[206] <Error>: 00809800 install_embedded_profile: Skipping the installation of the embedded profile Fri Mar 26 11:22:43 unknown mobile_installationd[206] <Error>: 00809800 verify_executable: Could not validate signature: e8008015 Fri Mar 26 11:22:43 unknown mobile_installationd[206] <Error>: 00809800 preflight_application_install: Could not verify /var/tmp/install_staging.6M55Ay/helloworld.app/helloworld Fri Mar 26 11:22:43 unknown mobile_installationd[206] <Error>: 00809800 install_application: Could not preflight application install Fri Mar 26 11:22:43 unknown mobile_installation_proxy[235] <Error>: handle_install: Installation failed Fri Mar 26 11:22:43 unknown mobile_installationd[206] <Error>: 00809800 handle_install: API failed Fri Mar 26 11:22:43 unknown mobile_installationd[206] <Error>: 00809800 send_message: failed to send mach message of 64 bytes: 10000003 Fri Mar 26 11:22:43 unknown mobile_installationd[206] <Error>: 00809800 send_error: Could not send error response to client

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• Read email from incoming mail server(POP)

  - by nccsbim071

  Hi, I have used an open source code from codeproject to read email from incoming mail server(POP Server). The code can be found at following location: http://www.codeproject.com/KB/IP/Pop3MimeClient.aspx So far it works fine i can read emails. My objective of using this code was to retrieve emails from POP server and process them. My problem is: If i use gmails pop server "pop.gmail.com" and run the appplication. I get only those emails that i have not retrieved since the last time i run the application. but if i use my clients pop server everytime i run the application i get all the emails in the pop server. for example: If i use gmail pop server: pop.gmail.com I have three emails in the pop server. I haven't run the application. I am running the application for the first time. Application reads the email, this time i will get 3 all the three email. I run the application second time, my application will not read any emails this time because i have already read the 3 existing one. This is fine, this is what i want. Now i send email to pop.gmail.com. I run the application again for the third time, this time i will only get the email that has just arrived that is the fourth one. This is good behaviour, this is what i want. But if i use my clients pop server: No matter how many times i run the application, it reads all the emails in the mail box. This will create problem for me, because i am thinking of building a window service that will read emails from pop server and process them. This service will run continuously. I will process emails in the pop serve then sleep for let's say 1 minute and the process the emails again. If the application downloaded from codeproject reads all the emails all the time, my clients mailbox can have like thousands for email in this mail box, so this would not be feasible for me. Is there some settings that is to be made at my client's pop server that will allow my application to retrieve only those emails that i have not read since last time i run the service or any help Please help, thanks,

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• Double Buffering for Game objects, what's a nice clean generic C++ way?

  - by Gary

  This is in C++. So, I'm starting from scratch writing a game engine for fun and learning from the ground up. One of the ideas I want to implement is to have game object state (a struct) be double-buffered. For instance, I can have subsystems updating the new game object data while a render thread is rendering from the old data by guaranteeing there is a consistent state stored within the game object (the data from last time). After rendering of old and updating of new is finished, I can swap buffers and do it again. Question is, what's a good forward-looking and generic OOP way to expose this to my classes while trying to hide implementation details as much as possible? Would like to know your thoughts and considerations. I was thinking operator overloading could be used, but how do I overload assign for a templated class's member within my buffer class? for instance, I think this is an example of what I want: doublebuffer<Vector3> data; data.x=5; //would write to the member x within the new buffer int a=data.x; //would read from the old buffer's x member data.x+=1; //I guess this shouldn't be allowed If this is possible, I could choose to enable or disable double-buffering structs without changing much code. This is what I was considering: template <class T> class doublebuffer{ T T1; T T2; T * current=T1; T * old=T2; public: doublebuffer(); ~doublebuffer(); void swap(); operator=()?... }; and a game object would be like this: struct MyObjectData{ int x; float afloat; } class MyObject: public Node { doublebuffer<MyObjectData> data; functions... } What I have right now is functions that return pointers to the old and new buffer, and I guess any classes that use them have to be aware of this. Is there a better way?

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• How best to store Subversion version information in EAR's?

  - by Rene

  When receiving a bug report or an it-doesnt-work message one of my initials questions is always what version? With a different builds being at many stages of testing, planning and deploying this is often a non-trivial question. I the case of releasing Java JAR (ear, jar, rar, war) files I would like to be able to look in/at the JAR and switch to the same branch, version or tag that was the source of the released JAR. How can I best adjust the ant build process so that the version information in the svn checkout remains in the created build? I was thinking along the lines of: adding a VERSION file, but with what content? storing information in the META-INF file, but under what property with which content? copying sources into the result archive added svn:properties to all sources with keywords in places the compiler leaves them be I ended up using the svnversion approach (the accepted anwser), because it scans the entire subtree as opposed to svn info which just looks at the current file / directory. For this I defined the SVN task in the ant file to make it more portable. <taskdef name="svn" classname="org.tigris.subversion.svnant.SvnTask"> <classpath> <pathelement location="${dir.lib}/ant/svnant.jar"/> <pathelement location="${dir.lib}/ant/svnClientAdapter.jar"/> <pathelement location="${dir.lib}/ant/svnkit.jar"/> <pathelement location="${dir.lib}/ant/svnjavahl.jar"/> </classpath> </taskdef> Not all builds result in webservices. The ear file before deployment must remain the same name because of updating in the application server. Making the file executable is still an option, but until then I just include a version information file. <target name="version"> <svn><wcVersion path="${dir.source}"/></svn> <echo file="${dir.build}/VERSION">${revision.range}</echo> </target> Refs: svnrevision: http://svnbook.red-bean.com/en/1.1/re57.html svn info http://svnbook.red-bean.com/en/1.1/re13.html subclipse svn task: http://subclipse.tigris.org/svnant/svn.html svn client: http://svnkit.com/

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• Calculating a Sample Covariance Matrix for Groups with plyr

  - by John A. Ramey

  I'm going to use the sample code from http://gettinggeneticsdone.blogspot.com/2009/11/split-apply-and-combine-in-r-using-plyr.html for this example. So, first, let's copy their example data: mydata=data.frame(X1=rnorm(30), X2=rnorm(30,5,2), SNP1=c(rep("AA",10), rep("Aa",10), rep("aa",10)), SNP2=c(rep("BB",10), rep("Bb",10), rep("bb",10))) I am going to ignore SNP2 in this example and just pretend the values in SNP1 denote group membership. So then, I may want some summary statistics about each group in SNP1: "AA", "Aa", "aa". Then if I want to calculate the means for each variable, it makes sense (modifying their code slightly) to use: > ddply(mydata, c("SNP1"), function(df) data.frame(meanX1=mean(df$X1), meanX2=mean(df$X2))) SNP1 meanX1 meanX2 1 aa 0.05178028 4.812302 2 Aa 0.30586206 4.820739 3 AA -0.26862500 4.856006 But what if I want the sample covariance matrix for each group? Ideally, I would like a 3D array, where the I have the covariance matrix for each group, and the third dimension denotes the corresponding group. I tried a modified version of the previous code and got the following results that have convinced me that I'm doing something wrong. > daply(mydata, c("SNP1"), function(df) cov(cbind(df$X1, df$X2))) , , = 1 SNP1 1 2 aa 1.4961210 -0.9496134 Aa 0.8833190 -0.1640711 AA 0.9942357 -0.9955837 , , = 2 SNP1 1 2 aa -0.9496134 2.881515 Aa -0.1640711 2.466105 AA -0.9955837 4.938320 I was thinking that the dim() of the 3rd dimension would be 3, but instead, it is 2. Really this is a sliced up version of the covariance matrix for each group. If we manually compute the sample covariance matrix for aa, we get: [,1] [,2] [1,] 1.4961210 -0.9496134 [2,] -0.9496134 2.8815146 Using plyr, the following gives me what I want in list() form: > dlply(mydata, c("SNP1"), function(df) cov(cbind(df$X1, df$X2))) $aa [,1] [,2] [1,] 1.4961210 -0.9496134 [2,] -0.9496134 2.8815146 $Aa [,1] [,2] [1,] 0.8833190 -0.1640711 [2,] -0.1640711 2.4661046 $AA [,1] [,2] [1,] 0.9942357 -0.9955837 [2,] -0.9955837 4.9383196 attr(,"split_type") [1] "data.frame" attr(,"split_labels") SNP1 1 aa 2 Aa 3 AA But like I said earlier, I would really like this in a 3D array. Any thoughts on where I went wrong with daply() or suggestions? Of course, I could typecast the list from dlply() to a 3D array, but I'd rather not do this because I will be repeating this process many times in a simulation. As a side note, I found one method (http://www.mail-archive.com/[email protected]/msg86328.html) that provides the sample covariance matrix for each group, but the outputted object is bloated. Thanks in advance.

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• How can I load a file into a DataBag from within a Yahoo PigLatin UDF?

  - by Cervo

  I have a Pig program where I am trying to compute the minimum center between two bags. In order for it to work, I found I need to COGROUP the bags into a single dataset. The entire operation takes a long time. I want to either open one of the bags from disk within the UDF, or to be able to pass another relation into the UDF without needing to COGROUP...... Code: # **** Load files for iteration **** register myudfs.jar; wordcounts = LOAD 'input/wordcounts.txt' USING PigStorage('\t') AS (PatentNumber:chararray, word:chararray, frequency:double); centerassignments = load 'input/centerassignments/part-*' USING PigStorage('\t') AS (PatentNumber: chararray, oldCenter: chararray, newCenter: chararray); kcenters = LOAD 'input/kcenters/part-*' USING PigStorage('\t') AS (CenterID:chararray, word:chararray, frequency:double); kcentersa1 = CROSS centerassignments, kcenters; kcentersa = FOREACH kcentersa1 GENERATE centerassignments::PatentNumber as PatentNumber, kcenters::CenterID as CenterID, kcenters::word as word, kcenters::frequency as frequency; #***** Assign to nearest k-mean ******* assignpre1 = COGROUP wordcounts by PatentNumber, kcentersa by PatentNumber; assignwork2 = FOREACH assignpre1 GENERATE group as PatentNumber, myudfs.kmeans(wordcounts, kcentersa) as CenterID; basically my issue is that for each patent I need to pass the sub relations (wordcounts, kcenters). In order to do this, I do a cross and then a COGROUP by PatentNumber in order to get the set PatentNumber, {wordcounts}, {kcenters}. If I could figure a way to pass a relation or open up the centers from within the UDF, then I could just GROUP wordcounts by PatentNumber and run myudfs.kmeans(wordcount) which is hopefully much faster without the CROSS/COGROUP. This is an expensive operation. Currently this takes about 20 minutes and appears to tack the CPU/RAM. I was thinking it might be more efficient without the CROSS. I'm not sure it will be faster, so I'd like to experiment. Anyway it looks like calling the Loading functions from within Pig needs a PigContext object which I don't get from an evalfunc. And to use the hadoop file system, I need some initial objects as well, which I don't see how to get. So my question is how can I open a file from the hadoop file system from within a PIG UDF? I also run the UDF via main for debugging. So I need to load from the normal filesystem when in debug mode. Another better idea would be if there was a way to pass a relation into a UDF without needing to CROSS/COGROUP. This would be ideal, particularly if the relation resides in memory.. ie being able to do myudfs.kmeans(wordcounts, kcenters) without needing the CROSS/COGROUP with kcenters... But the basic idea is to trade IO for RAM/CPU cycles. Anyway any help will be much appreciated, the PIG UDFs aren't super well documented beyond the most simple ones, even in the UDF manual.

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• How to show percentage of 'memory used' in a win32 process?

  - by pj4533

  I know that memory usage is a very complex issue on Windows. I am trying to write a UI control for a large application that shows a 'percentage of memory used' number, in order to give the user an indication that it may be time to clear up some memory, or more likely restart the application. One implementation used ullAvailVirtual from MEMORYSTATUSEX as a base, then used HeapWalk() to walk the process heap looking for additional free memory. The HeapWalk() step was needed because we noticed that after a while of running the memory allocated and freed by the heap was never returned and reported by the ullAvailVirtual number. After hours of intensive working, the ullAvailVirtual number no longer would accurately report the amount of memory available. However, this method proved not ideal, due to occasional odd errors that HeapWalk() would return, even when the process heap was not corrupted. Further, since this is a UI control, the heap walking code was executing every 5-10 seconds. I tried contacting Microsoft about why HeapWalk() was failing, escalated a case via MSDN, but never got an answer other than "you probably shouldn't do that". So, as a second implementation, I used PagefileUsage from PROCESS_MEMORY_COUNTERS as a base. Then I used VirtualQueryEx to walk the virtual address space adding up all regions that weren't MEM_FREE and returned a value for GetMappedFileNameA(). My thinking was that the PageFileUsage was essentially 'private bytes' so if I added to that value the total size of the DLLs my process was using, it would be a good approximation of the amount of memory my process was using. This second method seems to (sorta) work, at least it doesn't cause crashes like the heap walker method. However, when both methods are enabled, the values are not the same. So one of the methods is wrong. So, StackOverflow world...how would you implement this? which method is more promising, or do you have a third, better method? should I go back to the original method, and further debug the odd errors? should I stay away from walking the heap every 5-10 seconds? Keep in mind the whole point is to indicate to the user that it is getting 'dangerous', and they should either free up memory or restart the application. Perhaps a 'percentage used' isn't the best solution to this problem? What is? Another idea I had was a color based system (red, yellow, green, which I could base on more factors than just a single number)

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